The present invention relates to a method of and an apparatus for heating, melting and production of gaseous fuel.
Conventional methods of heating consist in fuel combustion and heat delivery to a material to be treated, by means of flame radiation and convection. Substantial disadvantages of the conventional methods are consumption of scarce kinds of fuel, nonuniformity of the temperature field and oxidizing atmosphere inside a furnace. Another conventional method is based upon the utilization of electric energy. Disadvantages of these methods are a low overall energy efficiency and nonuniformity of the temperature field.
A fluidized bed reactor provides a means for coal combustion and for distribution of heat generation in the space of the reactor. However, this reactor can be used only for heating of fine, lumpy materials. Heat generated in the fluidized bed can be extracted only in a chamber separated from that of combustion. The separation of the heat generation and extraction restricts application of such furnaces.
Uniform heating conditions and protective medium are achieved by heating in a liquid bath. However, energy efficiency of these furnaces is low, and they use gaseous or oil fuel.
The most conventional way of gas heating consists in combustion. However, combustion changes the gas composition. In many cases, combustion is based on the utilization of scarce oil and gas fuel. Gas heating can also be carried out without changing the chemical composition by heat transfer between a heat source and a heated gas. Heat can be extracted from combustion products of high temperature wastes. Another conventional method of gas heating consists in a heat exchange between gases: one of these gases is a heat receiver, whereas the other of the gases is a heat source. Heat can be transferred through ceramic or metal walls separating gas flows. This method is employed in boilers and recuperators. The drawback of such heating consists in the cost of material used for manufacturing gas exchangers and restrictions imposed on the temperature and pressure of a heated gas.
Another conventional method of gas heating consists in heat extraction from a heat source by a solid accumulator and heat transfer of this heat to a gas to be preheated. The implementation of this method by means of a periodical process is brought about in regenerators, caupers, stoves and similar devices. Continuously this method is brought about in heat exchangers with moving elements (as disclosed, for example, in R. Shchumann. Metallurgical Engineering, v.1, Addison-Wesley, 1952, p.p.132-133). High thermal resistance of a solid restricts possible amount of heat accumulated. The temperature of gas heating is restricted and the cost of construction is relatively high.
The general shortcomings of conventional gas heaters are their high cost, restricted temperature of preheating and impossibility to extract heat from all kinds of wastes, for example, from polluted gases, from slag and so on.
Uniform heating conditions and utilization of chemical energy of carbon are achieved in steel-making converters and open hearth furnaces. However, the amount of heat available in these reactors is limited by the chemical energy of carbon dissolved in pig iron. This restricts application of this method.
The amount of energy available in a reactor similar to a converter can be increased by simultaneous injection of coal and air (oxygen) into a melt. One example of such reactors is given in the U.S. Pat. No. 3,711,275. However, the heat evolved in the reactors disclosed in this patent can be supplied only to a material absorbed in a bath. Sensible heat of flue gases and part of chemical energy of CO cannot be used in these reactors, and can be recovered only by means of air and material preheating. These drawbacks prevent effective utilization of the above mentioned method of material heating, and the described reactor cannot be used for gas heating.